Timing Trouble

[MrGibbly]

I bought my 1978 L48 in October '03 and it has run pretty well since then. Up to this point I haven't done any engine work at all. Lately, it has gotten a little rough around the edges so I thought I'd take care of some simple stuff like plugs, wires, cap rotor, etc. Before I took anything apart I decided to check the timing but I'm having some trouble. I've never done this before so bare with me...

First, I disconnected the vacuum advance from the distributor and plugged the hose with a screw. Then I hooked up the timing light and fired her up. I found an angle where I could get a shot from between the radiator hose and the alternator that was clear. I had a very hard time finding a marking on the harmonic balancer and I couldn't get a reading. I gave up and crawled under the car (suck it in!) and smeared some spackling in the little groove in the harmonic balancer. That made it show up clear as day under the gun. However, the timing reading doesn't make any sense. When I start with the advance on the gun set at 0 the mark appears way at the "top" of the balancer. As I advance the dial on the light it works its way "down" until it is in the middle of the indicator affixed to the engine. The trouble is the light reads 46 degrees!!! Any help would be greatly appreciated.

 

[brusso]

May want to make sure that you are on the correct plug wire. If you were on the front plug, on the passenger side, #2 then you would be looking at the plug that fires 45 deg before #1 plug. (1-8-4-3-6-5-7-2-then 1 again)

 

[MrGibbly]

I appreciate you starting from the beginning with me on this one. To double-check: I'm leaning over the driver's side fender and clipping the inductive pickup to the wire coming from the farthest terminal towards the front of the car on my side of the distributor. I have a hard time following it but I'm pretty sure it runs to the #1 plug at the front of the block on the driver's side. There is a numeral 1 cast into the intake manifold directly above the plug this wire runs to. This reading can't be right the way I understand things because it would be so advanced the starter probably couldn't start it and it would be pinging itself to pieces. Any other thoughts?

 

[brusso]

Sounds like your in the right place. May want to check to see if the harmonic balancer "slipped". It's a heavy weight that is bound to it hub by rubber. Sometimes the rubber gives and the outer ring (that has the timing mark on it) slips around its hub.

 

[Hib Halverson]

As long as you are positive you've got your light triggering off #1, then I'd say your balancer's outer ring has slipped.

To confirm that, you need to verify the timing mark using the positive stop method. For that you need a degree wheel, a pointer (usually made from a piece of stiff wire) and a "stop plug" you screw into #1 plug hole.

Remove the dist. cap. Turn the engine over until the rotor points to the cap's #8 socket. Install the stop into #1 plug hole, turn the engine CW by hand until it stops. Mark the degree wheel where your pointer is. Turn the engine CCW until it stops again. Mark the degree wheel a second time.

Remove the stop. Turn the engine until the pointer reads exactly half way between the two marks in the area you were unable to sweep while the stop plug was installed. That's TDC #1 and your balancer mark should be within less than a degree of that. If it's not, the outer ring has probably slipped and you should replace the balancer.

 

[The73vetteman]

It's best to check the dwell before the timing. If the points gap is wrong it doesn't matter what you try to do with the timing.

If the dwell is right then you could do a static check of the timing. It's crude but tells you if you're in the ballpark. Just set the engine at about 12 BTDC and remove the distributor cap. The rotor arm should be pointing roughly to where the #1 plug lead runs from.

I think you could get a little more sophisticated by putting a lamp on the primary lead from the coil. When the points open the lamp will go out and that will tell you roughly when #1 would fire.

By the way, why did you disconnect the vac? I always leave this plugged in.

And one last point: when I first brought home my Vette and tried to time it I couldn't see the timing mark at all. In the end I found it by looking from the passenger side! The thing had so much advance I couldn't see it all from the drivers side.

Let us know if this helps at all.

'73

 

[MrGibbly]

The73vetteman, I don't think our cars are set up the same way. I believe yours has the older style points ignition (which I've never actually seen) and mine has the HEI (but not computer controlled) style. I shouldn't have to mess with dwell on an HEI at all, should I? At any rate, I have been disconnecting the line that leads to the little vacuum canister on the passenger side of the distributor and plugging it with a screw before I try to get a reading on the initial timing. From what I have read, I was expecting something in the neighborhood of 6 degrees. Then, full mechanical advance should be around 24-26 degrees? This little project was leading up to new plugs, wires, cap, rotor, coil and a recurve kit sometime this weekend... I expected to have some trouble but not this early! Hib Halverson, should I try and do the "stop method" you described myself or should I take it to my mechanic?

 

[The73vetteman]

You're probably right about not having points. I didn't notice the age of your car. I think I'd still do a quick check on the dist with #1 at 12 BTDC.

I thought full advance was around 36 degrees, but others may be better qualified to answer that.

You've never seen ponts ignition? Man do I feel old!

 

[MrGibbly]

The73vetteman...my car is a year older than I am. What I've read about my car indicates that in the stock set up it would start at 6 degrees and then go to 26 degrees at full mechanical advance (probably near redline). That is purported to be a part of why these cars were such underarchievers in terms of horsepower. The same documentation states that an initial timing of 12 degrees and a full mechanical advance to 36 degrees by 3,000 rpm would improve output considerably. So that's my motivation here! Do I need to replace my harmonic balancer or could I bolt on one of those covers that has the timining markings on it? Would they both be about the same amount of work since I'd have to pull everything off the front of the engine anyway?

 

[Vettehead Mikey]

I've seen more than one damper that has multiple marks on the outer rim, both GM and f_rd.

Set your engine at TDC on number 1 cylinder and see if there's another mark on the rim that aligns the TDC on the indicator plate.

 

[MrGibbly]

How do I set the engine to be at top dead center for the number one cylinder to see if any marks align with the indicator plate on the block? I've tried searching the surface of the balancer between what I thought was the marking (a groove in the surface all the way across balancer) and what would be about 50 degrees retarded from that point. There is one slightly reflective speck on the edge of one of the belt guides but nothing else that I can see. If I can set the engine to TDC on the #1 clylinder as you suggest could I just make a new mark that would be 0 degrees on the balancer and start from there?

 

[Vettehead Mikey]

See Hib's post above on how to find true TDC. If you then find another mark in the rim that corresponds to TDC you're all set. If not, you're best off getting a new damper assembly.

 

[JohnZ]

Step #1 - Find true TDC with a piston stop tool and mark it on the balancer.

Step #2 - Make sure the plug wires are indexed properly in the cap, and make sure you're putting the inductive pickup on the wire that's really the #1 wire.

With that as your baseline, you can do proper diagnosis.

 

[Jack]

Don't buy the fancy damper "cover" with the degree ticks ... it will cover your damper ... but if/when the outer (aka inertia) ring does begin to slip ... you won't see it because it'll be covered up. After 26 years it's not uncommon for original damper to slip.

If you do need a new damper ... try these guys: Motorville @ 1-888-463-0482 ... I find Gene more helpful than CJ. I just got a new ultralite damper for the race car ... not for street car ... it was under $40 and has all the tick marks. For street, they have 8" chrome under $38 and 8" black under $31.
JACK:gap

 

[brusso]

Don't buy the fancy damper "cover" with the degree ticks ... it will cover your damper ... but if/when the outer (aka inertia) ring does begin to slip ... you won't see it because it'll be covered up. After 26 years it's not uncommon for original damper to slip.
JACK:gap

THANKS MAN !!! I couldn't, for the life of me, remember what that ring was called.

 

[Hib Halverson]

The73vetteman, I don't think our cars are set up the same way. I believe yours has the older style points ignition (which I've never actually seen) and mine has the HEI (but not computer controlled) style. I shouldn't have to mess with dwell on an HEI at all, should I?

You are correct. A 78 has an HEI system and dwell is not adjustable.

Hib Halverson, should I try and do the "stop method" you described myself or should I take it to my mechanic?

Well...that depends on what level of mechanical skill you feel you have and if you have the tools/equipment I listed. I think, if you are comfortable with DIY service procedures more complicated than simply changing oil or spark plugs and you have the tools, you should try it. On the other hand, if you don't have a lot of skill or tools; I'd take it to a service shop. They can not only check for TDC but they can also replace the harmonic damper, if that's what ends up being required.

 

[MrGibbly]

Jack...thanks for the tip about the covers. I bet that chrome damper would look sweet but I can't imagine how hard it would be to see the timing ticks on it in the sunlight with the flashes from the timing light! This weekend, when I don't need "her" to take me to work, I'll get things sorted out. Thanks, everyone, for all your help! I think I can put the pieces together now!

 

[MrGibbly]

Hib, it looks like the only tool I am missing is the special puller tool for the harmonic balancer. Is that something I can probably find at Autozone or similar? Is it something I can get by without with a little improvization? I don't want to damage anything...but I do want to give this a whirl this weekend. I have to cut my teeth on something bigger than spark plugs and oil eventually! If I can't get it back together I can always have AAA take it to the shop for me Monday!

 

[brusso]

Yes, most auto parts stores have pullers that you can rent/buy. Just make sure you ask for one that can be used on a harmonic balancer. You don't want one that grabs the balancer from the outside edge. You want one that will bolt onto the holes provided on the hub of the balancer. The type that grabs, from the outside edge may pull off the inertia ring (I learned something new today) from the hub of the balancer. Not that you care if the old one gets wrecked, but you still have the hub stuck on there.

 

[Jack]

To install a damper, an install tool that presses damper onto crank snout is highly recommended ... there's been a lotta dampers pounded back onto the crank ... but that pounding is not good for the damper, crank or thrust bearings (rear main bearing). As said, if you remove a damper use a puller that bolts into damper's inner hub ... tip: slide a short 3/8" bolt into snout-hole ... that prevents puller shaft from ever coming near snout threads. A proper puller is widely available, an install tool isn't nearly so. Most shops/mechanics don't have an install tool ... well, nothing more than a block of wood and a five-pound sledge. Yes, you can pull the damper back onto the snout by screwing a succession of shorter bolts into the snout ... but that's real hard on the snout's threads. The proper install tool does thread into the snout, but the threads that are used to "close the gap" are on the other end of damper tool ... that way the damper tool's outermost threads get most of the abuse ... not the snout's threads. If you bugger-up snout threads you will have a big problem.

If your C3 has OE motor, especially if high mileage or lotsa age ... chances are the timing set (crank gear + cam gear + timing chain) and timing cover seal has lotsa wear and should be replaced. Damper has to be removed in order to get to seal or timing set. With damper off and water pump off ... it's relatively easy to get to seal/timing set. With finesse, luck and some choice words ... the timing cover can be wrangled back into place with no leaks. Keep this in mind if you plan to remove an sbc damper.
JACK:gap